The present invention relates to a power amplifier device that amplifies an input signal to a required voltage level.
For communication devices such as mobile phone terminals, important challenges are decreasing the chip area occupied by a power amplifier device and other built-in components and reducing the cost for them. For instance, Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2005-503679 (patent document 1) discloses a distributed power amplifier device for amplifying a radio frequency (RF) signal efficiently and at low cost.
The power amplifier device according to the above document comprises a plurality of push-pull amplifiers which are coupled on another to form a circular geometry. Input signals of equal amplitude but with opposite phases are input to adjacent amplifiers (transistors) in each push-pull amplifier. A closed loop formed by coupling the plurality of push-pull amplifiers functions as a primary winding. The power amplifier device further comprises a secondary winding adapted to the geometry of the primary winding. The secondary winding combines power output by each of the push-pull amplifiers efficiently.